The present invention relates to an apparatus and a method for cutting an inserted weft thread on a loom wherein the cutter is activated by a drive system that is completely separate from the main loom drive system.
As is well known in the fabric making art, after a length of weft thread has been inserted into the shed, it is severed from the weft thread supply by a cutting device. It is known, as evidenced by U.S. Pat. No. 4,134,434 and 4,531,555, to provide a cutting device which is mechanically driven by means of a cam system or the like from the main drive system of the loom. The cutter is thus driven synchronously with the loom operation.
Since the cutter system is mechanically coupled to the main drive of the loom, the time during the loom cycle that the weft thread is cut from the weft thread supply is fixed relative to the loom cycle. It is well known in the art that the optimal time for cutting a weft thread in relation to the loom cycle depends upon the type of weft thread that is being used. In the known devices, the use of different types of weft thread results in a compromise in the optimal cutting times, since the cutter is mechanically coupled to the loom drive. Thus, the known system render it impossible to optimize the cutting time for each particular type of weft thread.
In many cases, provision must be made for preventing the cutting of the weft thread from the weft thread supply where a weft thread insertion error must be remedied (see Dutch patent application 86 02 191). In these instances, the defectively inserted weft thread should not be severed from the weft thread supply. The insertion of the subsequent weft thread, which is still connected to the defective thread, will remove the defective weft thread from the loom. The known devices either mechanically lock the cutter device or keep the weft thread displaced from the cutter in order to prevent its being severed. The use of a separate device to mechanically lock the cutter or to displace the thread out of the cutter range serves to increase the complexity of the loom system.